Recording apparatuses, such as an inkjet printer, have been known as a liquid ejection apparatus in that liquid in a liquid chamber of a liquid ejection head is heated and ejected through a liquid ejection nozzle. In such an inkjet printer, ink droplets are ejected from respective nozzles arranged on an ink ejection surface on the bottom surface of a print head so as to form printed images, and a platen plate is arranged at a position opposing the ink ejection surface of the print head.
The platen plate defines the distance between the ink ejection surface and a recording sheet as an ejection object, which is conveyed by conveying means built in the inkjet printer, by supporting the recording sheet from the backside. The plate-like platen plate has a plurality of ribs (platen ribs) formed on the top surface at predetermined intervals in the width wise direction of the recording sheet so as to extend in the conveying direction of the recording sheet. In the inkjet printer having such a platen plate, the recording sheet supported with top faces of the ribs has been conveyed by the conveying means and printed by ejecting ink on the surface of the recording sheet from each nozzle.
However, in such an inkjet printer, when vertical and horizontal white spaces on a recording sheet are eliminated so as to perform so-called rimless printing or when a recording sheet smaller in size than that in established-size is used in mistake, excessive ink droplets are ejected across the periphery of the recording sheet, ink may attach the ribs of the platen plate so as to contaminate the plate, so that the ink attached on the platen ribs may contaminate the bottom surface of the recording sheet. Thus, for avoiding the contamination of the recording sheet bottom surface, it is necessary for the ribs of the platen plate not to have ink droplets attached thereon, so that a platen plate of such kind having a recess (ink receiver) formed on a region where ink droplets are attached for receiving ejected ink droplets has been known (see Japanese Unexamined Patent Application Publication No. 2000-118058 (P 3 to 4, FIGS. 2 and 3, or Japanese Unexamined Patent Application Publication No. 2002-86821 (P 4 to 5, FIGS. 1 and 2), for example).
However, techniques disclosed in Japanese Unexamined Patent Application Publication No. 2000-118058 and Japanese Unexamined Patent Application Publication No. 2002-86821 are applied to an inkjet printer having a so-called serial type print head, and they have been difficult to be applied to a printer having a line-type print head in that a number of nozzle rows are arranged over the entire width of a recording sheet. That is, in the printer having the serial type print head, ink droplets are ejected from each nozzle while the recording sheet is reciprocating in the width wise direction so as to form images on one region in a state that the recording sheet is stopped, and then, the recording sheet is conveyed in the conveying direction so as to form images on the next region after being stopped, so that the flatness of the recording sheet arranged under the ink ejection surface is no problem.
Whereas, in the printer having the line-type print head, while the recording sheet is conveyed, ink droplets are ejected from respective nozzles arranged in the width wise direction of the recording sheet so as to form images, so that in a state that the recording sheet conveyed under the ink ejection surface is not flatly supported, images may not be appropriately formed. In particular, in the case of a print head having ejection direction deflecting means for controlling to change the ejection direction of the ink droplets from each nozzle, the landing position of the ink droplet is deflected in the width wise direction of the recording sheet, so that the flatness of the recording sheet conveyed under the ink ejection surface needs to be secured.